Burner controller with safety cut-off



M y 1953 P. F. SWENSON El'AL 2,836,365

BURNER CONTROLLER WITH SAFETY CUT-OFF Filed April 6, 1955 1 O (I Hi) (1 United States Patent BURNER CONTROLLER WITH SAFETY CUT-OFF Paul F. Swenson, Cleveland Heights, and Myron T.

Cooperrider, East Cleveland, Ohio, assignors to Swenson Thermal Research, Inc., Cleveland, Ohio Application April 6, 1953, Serial No. 347,048

7 Claims. (Cl. 236-21) The invention relates to a new or improved liquid heater apparatus including an automatic control system for the apparatus.

The objects of the invention, particularly when embodied as a liquid heater of the class commonly known as a boiler for producing steam (the illustrated embodirnent), include provision of: a low cost, compact and efficient boiler unit for domestic and similar service; a gas fired, water coil type, boiler assembly capable of quickly producing water-free steam under substantial pressure for use in a battery of space heaters and in quantities sufficient for their efiectual steady operation, and a completely automatic control with adequate safety provision in event of derangement of heater equipment, failure of water supply and/or extinguishment of pilot light flame from any cause. More specific objects will become apparent from the following description of the illustrative arrangements shown in the accompanying drawings wherein:

Fig. 1 is a generally central longitudinal, fragmentary sectional and elevational assembly view showing the boiler unit and, diagrammatically or schematically, (and not in scale with the rest), one form of control apparatus for use with gaseous fuel.

Fig. 2 is a transverse sectional assembly view taken through a steam and water chamber'portion of the'unit as indicated at 22 on Fig. 1.

BOILER CONSTRUCTION As shown in Figs. 1 and 2 the body of the boiler unit A comprises a generally cylindrical hollow base portion 1, largely sheet metal, which houses a gas burner mechanism 13 and portions of the control apparatus for it (particularly those portions shown diagramly at the left); a similarly shaped and constructed tral, heater-coil-supporting or steam generating, heat hange section 2, and a top, generally cylindrical, ly sheet metal section 3, the latter containing an upright, steam and water separating drum 4 and providing, at the top wall of this section, a conventional fine or stack connection 5 above the drum. Drum 4, for brevity will hereinafter sometimes be called the separator drum or simply the drum.

More than half of the heat exchanger or water coil assembly 6 (for the sake of showing the remainder of the unit A in adequately large scale) is omitted from Fig. 1, together with the associated portions of the walls forming casing section 2.

Section 2 has generally concentric spaced apart, outer and inner wall members 8 and 9, embracing, for the full height of the section, an insulation body or fill it} of suitable mineral material around the coil assembly 6. Coil cleanout openings 3a and 9a are provided in the wall members 8 and 9, and a framework (not shown) is provided in member 8 for a removable, (e. g. separately insulated) closure member.

Lower and upper sheet metal wall members or frame 2,836,365 Patented May 27, 1958 plates 14 and 15 of approximately identical disc-like form are disposed at respective ends of easing section 2. These plates have annular ribs 14:: and 15a of channel shape-d cross section, flange portions of which telescope the outer and inner wall members 8 and 9, being suitably joined thereto. Thus, the plates 14 and 15 provide strong supports for the main casing section 2, coil assembly 6 and other portions of the unit, as is evident. The plates 12 and 15 are suitably perforated for receiving various parts, as evident from the drawing, and to allow, respectively, flow of secondary air upwardly to a gas burner head 26 of main burner mechanism B (two main burner heads 20 being shown) and flow of products of combustion from the generator section 2 into the top section 3. A gas pilot burner 21 is suitably arranged in igniting relationship to the main burner. Inspection and service openings in Wall members 8 and 9, adjacent the burner and control compartments have movable doors 8c and as shown at the lower left in Fig. 1.

The lower frame plate 14, which has to support the burner and all the heavier parts of unit A, is itself supported on legs 16 (e. g. three for stability) which lie inside and adjacent a skirt portion 8b of the outer casing member 8. The skirt portion forms, with a bottom-finishing stamping 17 and plate 14, a casing space or compartment 19 for the principal parts of the burner control equipment, to be described below (shown at left) and for the air and gas supply portions Zita and 26b of the main burner heads 29. Secondary air openings (not shown) are provided in suitable walls which form the compartment 19. Cushion pads or feet 18, below respective legs 16, rest on the floor of the building in which the apparatus is installed. The main burner members described above are suitably suspended from the plate 14, with the burner head portions 20 above said plate, adjacent to the water coil or steam generator assembly 6.

Generator or exchanger coil assembly 6 includes a distributor manifold casting 22 attached rigidly to casing section 2. The manifold receives condensate from the heaters served by the present unit, usually through a pump and reservoir apparatus, not shown; and the generator coils (three being shown at 23, 24 and 25) are connected in parallel to the manifold and, similarly, to an outlet header casting 26, extending through and supported by the upper frame plate 15. Header 26 has a steam outlet tube 28 leading through the bottom wall 29 of the drum 4 into the steam space or chamber 3% constituted by the upper portion of said drum. A

convection water return pipe or tube 31, extending loosely through the helices formed by the generator coils, connects a bottom, water containing portion of the drum 4 with the lower ends of all the coils of assembly 6 through the interior of the manifold 22.

As shown by comparison of Figs. 1 and 2 the discharge portion of the steam outlet tube 28 curves upwardly and laterally within the steam and water separa tion chamber (drum 4), the approximately horizontal open end portion 28a of the tube being directed generally tangentially of the vertical wall 32 of the drum or at an acute angle with respect to the portion of said wall which is intersected by the axis of tube portion 28a. Thereby, steam discharged from the tube, in impinging upon the drum wall, maintains the general body of steam in upper chamber space 30 in rotation, causing whatever water droplets are entrained by the steam to be separated therefrom by centrifugal action. Thus all the steam taken from the drum, as at one or more outlet pipes connected to the top wall 33 of the drum (one outlet shown at 34), is dry.

l action on the valve.

l at a 7 2,836,365 r When steam generation is first commenced by subjection of the coil assembly to fairly intense burner flame '(water in drum 4 then at low temperature) steam is apt to be delivered through the tube 28 to the cold drum as large bubbles, causing hammering as the bubbles are collapsed suddenly by the rapid condensing action ofthe cold water around the immersed portion of the tube. This can be reduced considerably, it not eliminated, by providing a small submerged outlet opening in the wall of the tube 28, preferably. on the inside or downward side of the curve in the tube, as at 34, so that a short convection path for warmed water to the return pipe 31 is afforded. With the opening 34 located as just mentioned, the buoyancy of the bubbles prevents discharge of steam through'the opening,

and the submerged relatively short path, by allowing water circulation by convection before the water in the drum has become uniformly warm, reduces the temperature diiterential between the first generated steam and the cold water around the tube 28'. V

' When the burnerhas to operate steadily at high'flame,

asin order to maintain the required head of steam'in extremely cold weather, the stack temperature tends 'to become undesirably high. In such cases the stack heat which would otherwise be wasted can be utilized to advantage in maintaining the necessary volume of steam by providing fins on the steam and'water drum for contact'with thecombustion products. An illustrative arrangement; of fins 36 is'shown on the bottom wall 29 and radial, vertically V extending fins 37 are shown on the side wall 32, coextensive therewith. The fins 37 are maintained generally out of contact with the upper casing wall 3 bysuitablemeans,

, of control; ista sleevehaving a one-way-yielding connec- V in order to avoid loss of steam heat and undesired overheating of wall 3. 7

Controls A float operated mechanism 40 shown schematically,

has a' lever 41 a portion of which controls makeup feedwater by engaging a'valve element 42 to admit water to thedrum 4 through a main-connected pipe 43. Normal water level in the drum, as at L, is thus established by float cludes a snap action valve 45 controlling the gas supply to the pilot burner 21; and when the, float is below the positionin which the makeup water valve is, for example,

- fully open (which could ordinarily occur only when there is negligible pressure in the feed water system)-,an arm portion 46 of the float levermoves the snap action valve 1 45 to closed position in order to block gasflow to the pilot burner 21.,

Thelprincipal V 7 comprises separate temperature-sensitive actuating elecoil assembly 6 in accordance with steam demand or V should be caused to shut down operation of the entire unit A in case of derangement of theburner mechanism and/ or in case of dangerously overheated-steam space, as from L lack of adequate water in the boilen Thearrangements a, according to Figs. 1 and 3 are operated through employ- .Vinent of scaled thermo-responsive vapor fluid generator apparatus of generally approved and accepted type, re-

quiring no outside source of power (e. g. electric current). Both arrangements fail safe in event of damage to any' portion of the vapor fluid containing parts' Control apparatus (Fig. I

The pilot burner temperature sensitive element (bulb 50 in Fig.1) is so located as to be renderedopenative solely as a'function of pilot flame heat (i. e. independent 7 of heat emanating from the main-'burner)- 'being in the updraft of secondary air to the burner and well below the main burner flame. Capillary tube 52 leads from the bulb The float controlled mechanism in control for the gas burnergmechanism B in the steam and water separator drum 4, for example somewhat above the normal water leveltherein as established by the float mechanism 40 earlier described; and its capillary tube 53 is also connected to bellows or diaphragm 54 V Y The gas valve GV has a singleport or controlpassage 58 with bottom and top seats for two plugs shown in the form of lower and upper valve discs 59 and 60 both flexibly con-' nected'to a common valve operating'member 61 which, in turn, is operated by a movable wall of the bellows 54 for simultaneous movement of the two valve discs by the bellows.

Principally for co-operation with a magnetic snap action device'70 (described later), provided in case on-off operation of the gas' valve control is necessitated by burner design limitations or for other. reasons, the valve-connected member 61 of the bellows 54, in the illustrated form tion with the bellows-'being held normally in abutment with its movable lower end wall by a very light compression spring 62 reacting at its'opposite endson sleeve 61 and 'an adjustable abutment 63 on a stem or rod 610, the upper end of which rod is fixedly attached to the bellows.

The rod 61a is held in approximately coaxial relationship V with the valve port 58 by a tension spring 64, the main pur poseof which will be explained below. The bore of the sleeve 61 is sufficiently larger than the rodto assure free dom of relative movement between sleeve and rod.

When the pilot light '21 is not burning, the lower valve 1 disc 59 is lifted, by atmospheric and gas pressure on'the bellows54, acting through spring 62 and sleeve 61, into closing relation to the gas port 58. The discs 59 and 60 which are shown in Fig. l in equally spaced relation to their seats-permitting maximum gas flowhave spherical floating connections 59a and 60a with the sleeve 61 "(held in position by a light spring 61b) 'so asto be self V equalizing on their valve seats in the-absence of accuments or thermostats which are, respectively, in heat asso- V ciation with the pilot burner 21 and the steam or equivalent temperature space of the boiler where invariations of temperature, hence pressure, will indicate that the burner B should increase or decreaseits heat output to the generator rately acting guiding means for the sleeve or the rod 61a t .such as would have some frictional restraint on the'valve positioning operation of the bellows.-

To enable modulating or gradual action of the bellows 54 in accordance with varyingfsteam temperatures as detected by the bulb 51 in drum 4 the inherent spring force of the bellows is adjustably biased by the spring which is secured at its lower end to the valve case as by a screw i 65. 'One end connection for the spring 64 is a free swivel V (not shown in detail).

V In order to enable a single motor device (bellowsjSd) to be subjected to relatively difierent vapor pressure effects of the two connected bulbs 50 and 51 at different times, as

- necessary for the desired fiully automatic controlling of the gas valve GV, the vapor generator, system isrpeculiar in that the bulb 50 which is-heated by the pilot flame has ap- V proximatelytwice the vapor fluid capacity or volume of that of the steam-temperature-detecting bulb 51; and the system is so charged with vapor fluid that, when neither bulb is subjected to higher than ordinary room temperature, a liquid-free space or, vacuum pocket, equivalent to thecapacity of bulb 51, is' present somewhere in the system; If, as one manner of charging the generator system with.

the proper amount of operating fluid, the bulb 51 is subjected to sufiiciently high temperature totvaporize all its contained'fluid; the bellows is collapsed against the force T exerted ,by its spring wall to a predetermined extent apbulb 51,; and the system is then sealed while holding as much liquified vapor fluid as it'will then contain, an ef- 'fective pocket of approximately the desired size will proximately equivalent to the volume or capacity of the exist in the system after sealing of it and when both bulbs are relatively cool. 7

The vapor fluid selected to charge generator system 50-54 is one with a higher temperature than water and whose vaporization curve is generally parallel to that of saturated steam. Monochlorobenzine is a suitable fluid. After installation, the effective size of the vacuum pocket" in the system can be varied by adjusting the tension of the spring 64; and that enables the valve discs 59 and 60 to be adjusted to occupy the illustrated maximum gas flow position when only the pilot-associated bulb St is heated by pilot burner flame to the necessary extent for vaporizing all the fluid that may be contained by that bulb (other bulb assumed cold as before commencement of main burner operation). Spring 64 actually serves principally as a means for setting the boiler apparatus for various steam output pressures as may be desired, since the pressure varies directly with temperature within the desired range of action of the system to 10 p. s. i. steam).

In operation, and as already referred to, when the pilot 21 is ignited, vaporization of all the fluid in bulb 50 causes expansion of the bellows 54 to position the valve discs 59 and 60 equidistantly from their valve seats, as illustrated. Thus ignition of main burner flame causes commencement of steam generation in coils 6; and, when the desired temperature (hence pressure) in the steam space of drum 4 has been reached, vaporization of fluid in bulb 51 takes place gradually, and the further expansion of bellows 54 results in movement of the upper valve disc 60 toward closed or gas-throttling position. By appropriate selection and/ or adjustment of spring forces (bellows wall and spring 64), assuming a burner design having a fairly high turn down ratio and that the heater equipment requirement for steam is more or less steady, as is usual, the main burner flame can be varied through a large range (high to low gas) by thermoresponsive action of bulb 51 so as exactly to meet the demand for steam or, in other words, the control system has true modulating or steady operation with varying volume output of steam.

When on-off main burner operation is desired, due to inadequate turn down ratio of the burner equipment or for any other reason, the magnetically acting toggle or snap action device 70, only generally referred to above, is adjusted to cause the upper valve disc 60 to snap shut despite the yielding restraint of the bellows and vapor generator fluid thereon (acting through spring e2 if the illustrated construction is used), when the valve disc 61? has reached a nearly closed position, that is the position below which it is no longer found practicable ot control the flame.

Snap action device 70, as shown is a permanent magnet couple one element (e. g. soft iron armature) 71 of which is carried by the valve-connected sleeve 61 and the other of which, (e. g. Alnico magnet 72) is suitably mounted in the valve body 55 for adjustment toward and away from armature element 71. An adjustment screw 74 is shown threaded into the body 55, beside the spring adjusting screw 65, and connected to the magnet 72. When the magnet is adjusted far enough below the lowermost desired position occupied by the valve-connected armature element 71, during modulating operation by the automatic controls, the magnet is then no longer capable of attracting element 71 with enough force to take control of the valve away from the restraining action of the vapor generator system motor 54. The yieldability aiforded by sleeve 61 and light spring 62 could be an inherent function of the generator system (through elasticity of vapor and that of the bellows wall).

The reason for the earlier described effective volume re lationship between bulbs 50 and 51 may now be readily understood from consideration of what would occur in case the pilot light is accidentally extinguished at a time when steam temperature in drum space 30 has reached 6 the desired point. The same condition, incidentally, can occur when pilot gas is cut ofl by float-controlled snap action valve after boiler operation has started and the steam temperature has reached such point. In either case, if the upper main gas valve disc 60 has been caused to close or nearly close in throttling the main gas sup ply, the pilot-associated bulb must have suflicient vapor fluid capacity to enable movement of the lower disc 59 through twice the distance it was moved by pilot-flame responsive action to the full-on position of the valve, before the lower disc can again close the valve. As the temperature in the steam space 30 drops, following extinguishment of pilot and main burner flame, the lower valve disc 59 continues to block passage of gas to the main burner, and upward pressure of the lower disc on its seat increases as the steam space, hence bulb 51, cools.

In event of rupture of any wall portion of the sealed vapor system, allowing steam or air to leak into the system, the released'spring force of the wall of bellows 54, augmented by connected tension spring 64, causes the upper valve disc quickly to shut off the main gas supply and thereafter to maintain the valve GV closed.

We claim:

1. In equipment of the character described, a heating apparatus adapted to contain a liquid to be heated, a main fluid fuel burner for supplying heat thereto, a fuel valve adapted to be moved to open and closed positions to control flow of fuel to the burner, a pilot burner, means normally tending to close the valve, a sealed vapor gen erator system including fluid motor means having a movable wall connected to the valve, said generator system including separate thermoresponsive bulb elements in heat association, respectively, with the pilot burner and with a varying temperature portion of said heating apparatus, respectively, said elements being operatingly connected continuously to the fluid motor means by confined fluid columns, respectively, so that the vapor pressure developed in both of the bulb elements is transmitted by the confined fluid to said fluid motor means from said bulb elements and is applied directly against the same side of said wall, the element associated with the pilot burner acting through the motor means on the valve in the direction to open the valve upon increase in pilot burner temperature and the element associated with said apparatus portion acting on the valve through the motor means in a manner to restrict flow of fuel to the main burner upon increase in temperature of said portion, said fuel valve comprising means forming valve port means having a pair of axially spaced seats, valve plug means having a pair of seats respective to those of the valve port means, said valve plug means being connected for simultaneous movement in one direction by the fluid motor means, the seats of one of said pairs of seats being spaced apart along the axis of the seats a distance greater than the seats of the other pair of seats, so that the operation of the fluid motor means in said one direction pursuant to heating the thermostatic bulb elements can cause full opening and then fuel restrictive closing or throttling of said valve port means.

2. The arrangement according to claim 1, wherein the motor means is a single flexible metal bellows, fluid conducting capillary tubes, respective to the bulb elements, connect the thermoresponsive bulb elements to the bellows, and the valve port means comprises means forming a single valve port and the valve plug means comprises two plugs coaxial with, and at opposite sides, respectively, of the port and connected for simultaneous movement in one direction by the bellows, the plugs being spaced apart along the port axis a distance greater than the eflective port length, so that operating movement of the bellows in said one direction pursuant to heating of the thermoresponsive bulb elements can cause full opening and then fuel-restrictive closing or throttling of said port.

3. The arrangement according to claim 1 wherein the motor means is a single flexible metal bellows, and fluid conducting capillary tubes, respective torthebulblelements, connect the thermoresponsive bulbue lements ,to the bellows; y r, f Y

4. The arrangement according to claim .3 further characterized in that adjustable spring. means are provided for normally urging the bellows to expanded position.

5., T he arrangement according to claim 3 characterized in that the connection between the bellows and the plug means, for effecting said simultaneous movement of the seats ofthe plug means, comprises a movable member which is movable relative to saidmovable wall of the bellows in a direction toward and away from said well and which has one portion operatively abutting said wall of the bellows so that the movable member is moved by the bellows, upon expansion of the bellows, and thereby moves saidplug means in said direction, a spring urges the movable member in the opposite direction, and

said plug means are mounted on said movable member for movement therewith, and for limited .universalrocking movement relative thereto. V V

6. The arrangement according to claim ltwherein the pilot-associated thermoresponsive bulb element has at least substantially twice as much vapor fluid operating capacity as the other bulb element has, and the. generator system includes spring means acting on the motor means to maintain, at normal temperature, a subatmospheric pressure pocket in the system approximately corresponding in volume to the capacity of said other bulb element,

:whereby, when the pilot-associated element is not subject to pilot burner heat and the other element is heated to an extent causing vaporization of all its contained fluid, cooling ot'thepilot-associated element can allow full closing ofthe fuel valve.

7[' The equipment according to-claim 1 characterized in that the pilot-associated .thermoresponsive bulb element has at least substantially twice as much vapor fluid operating capacity as has the other bulb element.

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